Math
posted by Abbey(Please help) .
Logs are stacked up in apile as shown in the figure. The top row has 15 logs and the bottom row has 21 logs. How many logs are in the stack?
a1= 1+14=15
an= 7+14=21
s1=(n/2)(a1+an)
(n/2)(15+21) = 18
How do I figure out the n?

Math 
Abbey(Please help)
Would n be 14?

Math 
Reiny
n/2(26) = 18
26n = 36
n = 36/26
something very wrong with your equation, since n has to a whole number
where does the 18 come from?
you seem to be using the formula
S(n) = n/2(first + last)
so 18 would be the sum of the logs ????
that makes no sense, since the bottom row alone contains 21 logs. 
Math 
Anonymous
No
Respond to this Question
Similar Questions

chem
"Yule logs are simulated wood logs make of compressed paper that burn with a red and green flame.How would you produce a similar yule log? 
Precalculus
.5=e^(20t) I am assuming this involves logs but we did't really learn logs. Anyone care to walk me through with a calculator. Have the Ti83 
Pre Cal (logs)
I need help with these logs 1: Log underscore4 16X 2: 2 Ln ( X(sqr. root)e 3:5^[2logUnderscore5(3x)] 4:log underscore2 ^[1280logunderscore2 5) I don't understand how to do them thanks 
Maths (Logs)
1. Write the following equation without logs log y = mx+ c This would be y = 10^(mx+c) right? 
math  natural logs
Find the EXACT solution to e^(1x) = 4^x You must use logs, not just a calculator. 
math logs
solve 3^(2x+1) = 9^(2x1) using base 3 logs 
algebra
200 logs are stacked so that 20 logs at bottom row 19 in the next ,18 in the next and so on.In how many rows can 200 logs be arranged and how many are there on the top row ? 
Physics
Raft made of 2.2m long pine logs.Average diameter of logs 26cm.How many logs are needed to strap together to build raft to hold max 4 people? 
Physics
Raft made of 2.2m long pine logs.Average diameter of logs 26cm.How many logs are needed to strap together to build raft to hold max 4 ? 
Physics
PART 1 Raft made of 2.2m long pine logs with Average diameter of logs 26cm.How many logs are needed to strap together to build raft to hold max 4 people?